Bronchial anatomy and single-lung ventilation in the pig

Purpose: To explore why two pigs died in the course of a study in which a d ouble-lumen tube (DLT) was used to achieve single-lung ventilation, the bro nchial anatomy of all six pigs involved in the study was examined at autops y. Methods: Autopsy involved examination of the lungs in situ and subsequent d issection of the lung tissue from the lobular bronchi. Results: All six pigs were found to have an apical robe (or lobular) bronch us arising from the trachea. In three it was on the right, as is usual in p igs, and in three, including the two that died, it was on the left. The mai nstem bronchi to both lungs were short in all pigs, with major segmental br onchi arising just distal to the carina. Conclusion: The bronchial anatomy of the pig is such that the inflated cuff s of commercially available DLTs may cause partial or complete obstruction of the apical bronchi of one or both lungs, regardless of the side of the t racheal bronchus. The transmission of the resulting breath sounds across th e narrow pig thorax can make auscultation unhelpful in assisting with optim al tube placement.